JPH0374658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing maleimides. Maleimide compounds are used as raw materials for resins, pharmaceuticals,
The present invention provides an advantageous method for producing the compound, which is used as a raw material for agricultural chemicals and the like.

[Prior Art] Methods for producing maleimides have been studied for a long time.

The most common method is to produce maleimide by dehydrating maleamic acid using a dehydrating agent such as acetic anhydride, which is also disclosed in US Pat. No. 2,444,536. .

That is, it is a method in which maleic anhydride and an amine compound are reacted, and the resulting maleamic acid is dehydrated and ring-closing imidized in the presence of acetic anhydride and sodium acetate. This method requires an equivalent amount of expensive acetic anhydride to maleamic acid in the imidization reaction, and also requires a large amount of water when separating and recovering maleimide produced from the liquid after the imidization reaction. As a result, a large amount of wastewater containing acetic acid is produced, which has the disadvantage of requiring a large amount of cost to detoxify it. For this reason,
This method is too expensive to industrially produce imide compounds.

Also, as in the specification of Japanese Patent Application Laid-Open No. 53-68770,
A method of reacting maleic anhydride with an amine compound in an organic solvent and carrying out a dehydration ring-closing reaction in the coexistence of an aprotic polar solvent such as dimethylformamide or dimethyl sulfoxide and an acid catalyst without isolating the maleamic acid produced. There is also. However, this method requires a large amount of expensive and toxic aprotic polar solvents such as dimethylformamide, which increases the production cost of maleimide. There are problems such as increased loss due to deterioration of the solvent, and furthermore, it is difficult to remove these aprotic polar solvents from the product maleimide due to their high boiling points. Therefore, it cannot be said that it is an excellent method.

Furthermore, as disclosed in Japanese Patent Publication No. 51-40078, solvents such as toluene, xylene, and chlorobenzene having a boiling point of 80°C or higher and chlorosulfonic acid, p-toluenesulfonic acid, and benzenesulfone are used as diluents. There is also a method of carrying out thermal dehydration ring closure with an acid catalyst such as orthophosphoric acid, pyrophosphoric acid, phosphorous acid, etc., and distilling the water produced at this time out of the system by azeotropy with the solvent. Compared to the above two methods, this method not only does not require large amounts of expensive dehydrating agents such as acetic anhydride, but also
It is excellent in that the maleimide produced is easy to separate and recover.

However, this method uses relatively many expensive acid catalysts such as chlorosulfonic acid, p-toluenesulfonic acid, benzelsulfonic acid, orthophosphoric acid, pyrophosphoric acid, phosphorous acid, etc. The yield is also low and it is not economically satisfactory as an industrial production method.

On the other hand, JP-A-54-30155 discloses a method for producing oligoimides using a mixture of an inorganic or organic acid-containing acid and a quaternary ammonium salt of this acid as a catalyst.

However, the quaternary ammonium salt used in combination with an acid catalyst in this method is an ammonium salt in which the nitrogen atom is substituted at least twice, such as dimethyldialkyl ammonium methanesulfonate, methanesulfonic acid, tetraoctylammonium, etc. is an expensive phase transfer catalyst. Therefore, the use of such compounds is too expensive.

In this method, it is essential to limit the ratio of the acid catalyst to the quaternary ammonium salt within a certain range in order to maintain a good imidization yield. However, since the ratio of these catalysts changes once used in the reaction, it is not possible to obtain a good imidization yield even if the catalyst is used again as it is.

Therefore, in order to use the catalyst again, there is a problem in that a great deal of effort is required to maintain and manage the catalyst activity, such as refining and adjusting the catalyst.

[Problem that the invention seeks to solve]

Such currently existing methods for producing maleimides have many problems and are not satisfactory for industrial implementation.

Thus, an object of the present invention is to provide a method for producing maleimides with higher purity in a complete and simple manner and at low cost compared to the above-mentioned methods.

[Means for solving problems]

The present inventor has long continued research on synthetic reactions of maleimides. In particular, as a result of intensive studies on catalysts used in the ring-closing imidization reaction, we found that the mixture of amine salt and acid produced by the neutralization reaction between the raw material amine of maleimides and the acid is water-insoluble or water-immiscible. We have completed the present invention by discovering that the present invention exhibits a catalytic action with extremely high selectivity for ring-closing imidization reactions in inert organic solvents.

Conventionally, it was believed that strong organic or inorganic acids exhibit the best catalytic action for ring-closing imidization reactions, so a mixed catalyst system of an amine salt and an acid produced by a neutralization reaction with such an acid has been developed. It must be said that it is completely surprising that the present invention shows a selectivity superior to that of conventionally used acid-only catalyst systems.

That is, the present invention provides an amine salt obtained from the raw material amine and an inorganic or organic acid as a catalyst when producing maleimides by dehydrating and ring-closing maleamic acid obtained from maleic anhydride and amines, and Maleamic acid is dissolved in a water-insoluble or water-immiscible inert organic solvent using a mixed catalyst consisting of a mixture with an inorganic or organic acid and having an amine salt content of 40 to 80 mol % in the mixture. This is a method for producing maleimides, characterized by heating and ring-closing imidization reaction.

The most characteristic feature of the present invention is that in the ring-closing imidization reaction, sulfuric acid, orthophosphoric acid, pyrophosphoric acid,
Instead of an acid catalyst such as p-toluenesulfonic acid, an amine salt produced by a neutralization reaction between an amine used as a raw material during the production of maleimides and an inorganic or organic monobasic acid or polybasic acid is used. It consists in using an inorganic or organic monobasic acid or a mixture with a polybasic acid as a catalyst.

Further, in some cases, a metal-containing compound or a stabilizer may be present in the ring-closing imidization reaction.

The maleamic acid used in the present invention is usually easily obtained by the reaction of maleic anhydride and primary amines, and is represented by the following general formula.

[In the formula, R is selected from an alkyl group having 1 to 20 carbon atoms, a phenyl group, a benzyl group, a cyclohexyl group, a pyridyl group, a quinolyl group, and those in which these groups are substituted with halogen, carboxyl group, or nitro group. It is something that can be done. In particular, the following primary amines are suitable as raw materials for the maleamic acid used in the present invention.

Methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,
sec-butylamine, tert-butylamine, n-
hexylamine, n-dodecylamine, allylamine, benzylamine, cyclohexylamine,
Aniline, nitroaniline, aminophenol,
Aminobenzoic acid, anisidine, ethoxyphenylamine, monochloroaniline, dichloroaniline, toluidine, xylidine, ethylaniline, etc.

The synthesis of maleamic acid takes place almost stoichiometrically, with 1 mole of maleic anhydride producing 1 mole of amine.
mol is preferred, but 0.8 to 1.5 mol, preferably 0.9 to 1.5 mol
It is possible to react within the range of 1.2 mol. If the amine compound is in excess of maleic anhydride, it is necessary to use a larger amount of acid catalyst than necessary when directly subjecting it to the imidization reaction, and side reactions may be generated in the imidization reaction. The above range is preferable since a large amount of substances are produced and the yield of the imidization reaction becomes low.

Furthermore, the organic solvent used in the present invention is preferably a solvent that is insoluble or immiscible in water, inert, and does not participate in the reaction, such as benzene, toluene, petroleum fractions with a boiling point of 50 to 120°C, xylenes, etc. Ethylbenzene, isopropylbenzene, cumene, mesitylene, tert-butylbenzene, pseudocumene, trimethylhexane, octane, tetrachloroethane, nonane, chlorobenzene, ethylcyclohexane, petroleum fraction with a boiling point of 120-170°C, m-dichlorobenzene, sec -Butylbenzene, p-dichlorobenzene, decane, p-
Examples include cymene, o-dichlorobenzene, butylbenzene, decahydronaphthalene, tetrahydronaphthalene, dodecane, naphthalene, cyclohexylbenzene, and petroleum fractions with a boiling point of 170 to 250°C. The amount of this solvent to be used is 1 to 20 times (volume), preferably 3 to 7 times the amount of maleamic acid, in order to conduct the reaction smoothly and satisfy economic conditions.
Double amount used.

Further, a maleimide having a boiling point suitable for the reaction conditions is selected while taking into account the solubility, price, ease of handling, etc. of the maleimide. Furthermore, when considering the separation of the maleimide from the solvent after the reaction is completed, it may be advantageous to use a low boiling point solvent and carry out the reaction under pressure.

As a catalyst, sulfuric acid, p-toluenesulfonic acid,
By neutralizing inorganic or organic monobasic acids or polybasic acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, benzenesulfonic acid, and trichloroacetic acid with amines, which are raw materials for the production of maleimides. amine salts and mixtures thereof with inorganic or organic monobasic acids or polybasic acids are used.

Good results can be obtained if the amine salt component is present in the mixed catalyst in an amount of 40 to 80 mol %.

The amount of mixed catalyst used is 2 to 400 mol%, preferably 20 to 200 mol%, based on maleamic acid.
is within the range of

Further, depending on the case, a metal-containing compound and a stabilizer may be allowed to coexist in the reaction.

Since the mixed catalyst system of amine salt and acid produced as described above does not dissolve in the organic solvent used in the present invention, the reaction system is essentially separated into two layers: an organic layer and a catalyst layer. . This state is the same during the reaction and at the end of the reaction, and in addition, the mixed catalyst system of an amine salt and an acid as a catalyst does not substantially change before and after the reaction. Therefore, the mixed catalyst system itself can be used as is without recovery or purification in the next reaction.

When using this catalyst layer for the next reaction, the organic layer after the reaction and the catalyst layer may be separated at a temperature in the range of 120 to 250°C and the catalyst layer may be used as it is for the next reaction, or the catalyst layer may be used as it is for the next reaction. The layer may be mixed with 5 to 20% water by weight to lower the temperature and viscosity and may be added in the form of an aqueous solution for easy handling.

Further, depending on the case, a metal-containing compound or a stabilizer may be allowed to coexist in the reaction system for the reaction. The metal-containing compound used at this time is at least one metal oxide, acetate, maleate, succinate, or nitrate selected from the group consisting of zinc, chromium, palladium, cobalt, nickel, iron, and aluminum. , phosphates, chlorides and sulfates, among which zinc acetate is particularly effective. The amount of these used is 0.005 to 1 mole of maleamic acid as metal.
It is 0.5 mol%, preferably 0.01 to 0.1 mol%.

Furthermore, as a stabilizer, methoxybenzoquinone,
p-methoxyphenol, phenothiazine, hydroquinone, alkylated diphenylamines, methylene blue, tert-butylcatechol, tert-
Butylhydroquinone, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, thiodipropionic acid esters, mercaptobenzimidazole, triphenylphosphite, alkylphenols, alkylbisphenols, and the like are used.

The effect of these stabilizers is to allow the maleimidization reaction produced by the imidization reaction to exist stably without deterioration under the high temperature conditions.

As for the amount added, adding a trace amount will have little effect, and conversely, adding an excessive amount is not desirable because it may cause a problem of mixing into the product. Therefore, the amount of these used is 0.005 to 0.5 mol%, preferably 0.05 to 0.3 mol%, based on 1 mol of maleamic acid.
It is mole%.

As a method of carrying out the present invention, first, an amine compound is added to a solution of maleic anhydride in an organic solvent,
Maleamic acid is obtained by reacting at 150°C or lower, preferably 30-120°C, for 15-120 minutes. Next, without isolating the maleamic acid, the above-mentioned mixed catalyst of salt and acid or a mixed catalyst layer of salt and acid separated from the reaction system is added, and if necessary, a metal-containing compound and/or Add stabilizer and heat at 120-250℃, preferably 130-220℃.
Maleimides can be produced in high yield by heating for ~15 hours and performing the reaction while distilling the generated water out of the system by azeotropic distillation, or by distilling it out of the system after the reaction is completed. can do.

The present invention has been described above, and the advantages obtained by the present invention are as follows.

A mixed catalyst system of amine salts and acids produced by the neutralization reaction of amines, which are raw materials for the production of maleimides, and inorganic or organic monobasic acids or polybasic acids is effective for ring-closing imidization reactions. Since it has a highly selective catalytic action, it is possible to obtain highly pure maleimides in high yields.

Since the mixed catalyst system of amine salt and acid used as a catalyst is stable and can be used repeatedly in the reaction, the cost of the catalyst can be almost ignored.

Since the catalyst is used repeatedly, there is virtually no need to treat the used catalyst to make it non-polluting, and since it is a closed system, there is no need to worry about environmental problems caused by disposing of the catalyst.

As described above, maleimides can be produced cheaply, safely and easily.

The present invention will be explained in more detail below with reference to Examples.

Example 1 Oxoxylene 100 in a 300 c.c. Meyer flask
g and 60 g of orthophosphoric acid were dispersed. Next, while cooling the Mayer flask in a water bath, 37 g of cyclohexylamine was added dropwise to obtain a white xylene slurry solution as a mixed catalyst of orthophosphoric acid monocyclohexylamine salt and orthophosphoric acid.
The amount of amine salt in this mixed catalyst is 60.9 mol%.
It is.

On the other hand, 100 g of ortho-xylene was charged into a flask equipped with a thermometer, a cooling tube equipped with a water separator, a dropping funnel, and a stirrer, and 100 g of maleic anhydride was added to the flask.
g was added thereto, the temperature inside the flask was raised to 100°C, and the maleic anhydride was dissolved.

Then, a solution of 100 g of cyclohexylamine dissolved in 600 g of ortho-xylene was added dropwise over 1 hour with stirring to synthesize a slurry of N-cyclohexylmaleamidic acid in oxoxylene.

Next, the total amount of the mixed slurry of the above amine salt and orthophosphoric acid (the amount of the mixed catalyst corresponds to 60.7 mol% with respect to maleamic acid) and 0.1 g of copper diptyldithiocarbamate are added to this slurry.
was added, heated and maintained at 143° C. with stirring, and allowed to react for 7 hours while distilling water produced by the reaction out of the system together with oxoxylene. After the reaction
The lower catalyst layer was separated and removed from the reaction solution at 143°C.

Subsequently, the temperature of the reaction solution was lowered to 60° C., 100 g of water was added, and the mixture was stirred and washed with water for 30 minutes, and the aqueous layer was separated. After repeating this operation twice, 10mmHg from the organic layer is removed.
Oxoxylene (abs) was distilled off under reduced pressure.

Next, 0.3 g of copper dibutyl dithiocarbamate was newly added to the flask, and N-
Distillation of cyclohexylmaleimide was carried out. As a result, 171 g of bright white crystals of N-cyclohexylmaleimide were obtained. The purity of this stuff is 99.8
The yield is 94.4 mol% based on the raw material cyclohexylamine.

Next, the reaction operation was repeated in exactly the same manner except that the catalyst layer separated from the reaction system was used as a catalyst, and 171 g of bright white crystals of N-cyclohexylmaleimide were obtained. The purity of this thing is
The yield was 99.8% by weight, corresponding to 94.4% by mole based on the raw material cyclohexylamine.

Example 2 100 g of p-cymene and 100 g of orthophosphoric acid were dispersed in a 300 c.c. Meyer flask. Next, while cooling the Mayer flask in a water bath, 56 g of n-butylamine was added dropwise to obtain a mixed white slurry solution of butylamine salt of orthophosphoric acid and orthophosphoric acid. The amount of amine salt in this mixed catalyst is
This corresponds to 75.0 mol%.

On the other hand, a reactor equipped with a glass flask thermometer, a stirrer, and a water separator was prepared.

Next, 53 g of maleic anhydride powder was added to 50 g of p-cymene.
The solution dissolved in g was charged into the above reactor. Next, the temperature inside the reactor was adjusted to 130°C, and a solution of 40 g of n-butylamine dissolved in 400 g of p-cymene was added dropwise over 30 minutes to produce N-(n-butyl).
A slurry liquid of maleamic acid was synthesized.

To the slurry liquid thus obtained, the entire amount of the mixed catalyst slurry liquid (the amount of the mixed catalyst corresponds to 186.5 mol% based on maleamic acid), zinc acetate.
0.034g and p-methoxyphenol 0.0065g
was added and reacted at a temperature of 180° C. for 3 hours while distilling off the produced water together with p-cymene. The weight of the reaction solution after the completion of the reaction was 620g, and N
The concentration of -(n-butyl)maleimide was measured to be 11.5% by weight, which corresponds to 85.1% by mole based on the raw material n-butylamine.

Subsequently, the reaction operation was repeated in exactly the same manner except that the catalyst layer separated from the reaction system was used, and 625 g of the reaction liquid was obtained. N-(n-butyl) in this
The concentration of maleimide was determined to be 11.6% by weight, which corresponds to 86.5% by mole.

Example 3 60 g of orthophosphoric acid in a 300 c.c. Meyer flask
I put it in. Next, 46 g of cyclohexylamine was added dropwise to the Mayer flask while cooling it in a water bath to obtain a sticky mixed catalyst slurry of cyclohexyl monoamine phosphate and phosphoric acid.
The amount of amine salt in this mixed catalyst is 75.8 mol%.
It is.

On the other hand, 100 g of xylene was charged into a glass autoclave equipped with a thermometer, a cooling tube, a dropping funnel, and a stirrer, and 100 g of maleic anhydride was added thereto.
was added to raise the temperature inside the flask to 100°C to dissolve maleic anhydride.

Next, add cyclohexylamine to 400g of xylene.
A solution containing 100 g of N-cyclohexylmaleamic acid was added dropwise over 30 minutes with stirring to synthesize a slurry of N-cyclohexylmaleamic acid in the above solvent.

Next, add the entire amount of the mixed catalyst slurry to the slurry liquid (the amount of mixed catalyst is based on maleamic acid).
(equivalent to 60.7 mol %) was added and heated in a closed system without distilling water out of the system to maintain the internal temperature at 152°C and react for 3 hours. The pressure in this time series was 1.2 atm at the beginning of the reaction, but after 3 hours it was
It became 7.0 atm.

After the reaction was completed, it was cooled to an internal temperature of 130°C, and then
When the pressure was returned to normal and the reactant was taken out and allowed to stand, the reaction solution was clearly separated into two layers: an organic layer and a catalyst layer.
The weight of this organic layer is 660g, and N-
The cyclohexylmaleimide content was 24.6% by weight as determined by gas chromatography. This is for the raw material cyclohexylamine.
This corresponds to 89.8 mol%.

Subsequently, the same procedure was repeated except that a mixed catalyst layer of amine salt and acid separated from the reaction system was used, and 664 g was obtained as an organic layer. The N-cyclohexylmaleimide content in this was 24.5% by weight. This corresponds to 90.0 mol% based on the raw material cyclohexylamine.

Comparative Example 1 99.2 g of cyclohexylamine was added to a solution of 98 g of maleic anhydride dissolved in 500 g of toluene with stirring.
It was added dropwise at 50-70°C. Stir for 2 hours after completion of dropping,
N-cyclohexylmaleamic acid was obtained. Subsequently, 14 g of methanesulfonic acid, 8.7 g of methanesulfonic acid-N-cyclohexylmaleamide, and 15 g of N-methylpyrrolidone were added to this solution, and the resulting water was refluxed at 115°C for 3.5 hours as an azeotropic distillate with toluene. I reacted while removing it.

Thereafter, 15 g of acetic anhydride was added and the mixture was allowed to react for 30 minutes, after which the temperature was lowered to 60° C. and the reaction mixture was filtered to remove insoluble impurities, catalyst, unreacted N-cyclohexylmaleamic acid, and the like. followed by liquid
200 g of water was added, stirred and washed with water for 30 minutes, and the aqueous layer was separated. After repeating this operation twice, toluene was distilled off from the organic layer under reduced pressure of 30 mmHg (abs), yielding 172 g of a colored solid containing cyclohexylmaleimide. According to GPC analysis, the content of N-cyclohexylmaleimide was 10.0% by weight, and the yield of N-cyclohexylmaleimide was 9.6% by mole based on cyclohexylamine. The results of gas chromatography analysis of the reaction solution also showed similar yields.

Comparative Example 2 In the method of Comparative Example 1, 73 g of n-butylamine was used instead of cyclohexylamine, 14 g of methanesulfonic acid and 8.4 g of methanesulfonic acid tributylamine salt were used as reaction catalysts, and N was used as a polar solvent.
The reaction was carried out in exactly the same manner except that dimethylformamide was used in place of methylpyrrolidone, and 151 g of a colored oily liquid containing N-n-butylmaleimide was obtained.

According to GPC analysis, the content of N-n-butylmaleimide was 13.4% by weight, and the yield was 13.2% by mole based on the raw material n-butylamine.

Furthermore, analysis by gas chromatography of the reaction solution after washing with water revealed that the yield was similar.

Comparative Example 3 43.1g of maleic anhydride was mixed with 331.8g of chlorobenzene.
39.7 g of cyclohexylamine in a solution dissolved in
was added and reacted at 40°C for 1 hour.

Dimethylacetamide 12 was added to the resulting slurry of N-cyclohexylmaleamide acid.
cc and 2 g of trichloroacetic acid were added, heated to 135°C, and reacted for 6 hours while removing water produced by the reaction together with the solvent.

After the reaction was completed, 402 g of the reaction solution was collected. Analysis of N-cyclohexylmaleimide in this reaction solution by gas chromatography revealed that it contained 2.2% by weight of N-cyclohexylmaleimide.

The yield of N-cyclohexylmaleimide was equivalent to 12.3 mol% based on the raw material cyclohexylamine.

Comparative Example 3 A mixed catalyst was obtained in exactly the same manner as in Example 1, except that 7 g of cyclohexylamine was used when preparing the mixture of orthophosphoric acid monocyclohexylamine salt and orthophosphoric acid. The content of amine salt in this mixed catalyst was 11.5 mol%.

When this catalyst was used for a reaction, many white crystals were deposited on the catalyst layer that was separated into the lower layer after the reaction, and analysis of this substance using an infrared absorption spectrum revealed that it was fumaric acid. From this, it is clearly predicted that many side reactions occur in the reaction.

Finally, 102 g of white crystalline N-cyclohexylmaleimide with a purity of 99.8% by weight was obtained, which corresponds to a yield of 56.8 mol% based on the starting material cyclohexylamine.

Comparative Example 4 The same procedure as in Example 1 was carried out except that only 60 g of orthophosphoric acid was used, and 83 g of white crystal N-cyclohexylmaleimide was obtained. This is for the raw material cyclohexylamine.
This corresponds to a yield of 45.8 mol%.

Furthermore, the appearance of the catalyst layer after the reaction was the same as in Comparative Example 3.

Comparative Example 5 A mixture of orthophosphoric acid monochloroaniline salt and orthophosphoric acid obtained by reacting 60 g of orthophosphoric acid and 47 g of 0-chloroaniline instead of the mixture of orthophosphoric acid monochlorohexylamine salt and orthophosphoric acid in Example 1. The same procedure was carried out except that N-cyclohexylmaleimide was used as a catalyst, and 80 g of white crystalline N-cyclohexylmaleimide was obtained.
This corresponds to a yield of 44.3 mol% based on the raw material cyclohexylamine.

Claims (1)

[Claims] 1. When producing maleimides by dehydrating and ring-closing maleamic acid obtained from maleic anhydride and amines, an amine salt obtained from the raw material amine and an inorganic or organic acid is used as a catalyst, and an inorganic or organic acid. A ring-closing imidization reaction is carried out by heating maleamic acid in a water-insoluble or water-immiscible inert organic solvent using a mixed catalyst consisting of a mixture of and having an amine salt content of 40 to 80 mol%. A method for producing maleimides, which comprises: